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-   -   Steer tube (https://www.bikeforums.net/bicycle-mechanics/602159-steer-tube.html)

BCRider 11-16-09 03:45 AM

Road Fan, if they ovaled the thread on a threaded tube then they did you a mis-service since you're now going to have a helluva time threading on the upper headset. Similarly on adding a "complimentary" bend to make your tube form an S curve instead of actually making it straight. An S curve will totally screw up the critical alignment required to get the upper and lower headset bearings to work smoothly and provide proper support. If that tube is not dead on straight or at least near straight to a close tolerance then your headset bearings will not share the load over the total complement of bearing balls. This will make for a notchy feeling steering. This will tend to make you not preload the bearings to the correct level since doing so will result in a notchy or rough feel. And trust me, having had to true up a frame head tube that had out of parallel cup seating surfaces that produced the same out of plane notchiness I know this really sucks. Hopefully they are explaining the results badly and the tube is OK. While it may seem fine to the naked eye the final test will be when you go to add the correct amount of preload to the bearings and if the fork now swings freely. If you find you need to significantly reduce the preload to avoid notchiness then you can bet that it's either still curved or has an S bend in it.

Keeping my fingers crossed that it's good......

Road Fan 11-16-09 11:28 AM

I think I've caused confusion:

They didn't actually create a zig-zag, they straightened it very well.

I de-ovalized the thread area.

I just finished installing the fork into the frame, and every thing did thread well. No binding, and it's real smooth.

Perhaps a bit rough but usable, good enough to test out the bike's geometry.

I think I got it dimensionally pretty darn close to original!

illwafer 11-16-09 08:11 PM

if anyone cares, i straightened a steerer tube by inserting it between some tree branches and putting all my weight on it several times. i barely moved it anywhere, but i got it pretty close. it works fine, and i'm not worried about a catastrophe since i know how strong it is.

BCRider 11-16-09 08:40 PM

Quote:

Originally Posted by Road Fan (Post 10037646)
I think I've caused confusion:

They didn't actually create a zig-zag, they straightened it very well.

I de-ovalized the thread area.

I just finished installing the fork into the frame, and every thing did thread well. No binding, and it's real smooth.

Perhaps a bit rough but usable, good enough to test out the bike's geometry.

I think I got it dimensionally pretty darn close to original!

Sounds like a "WELL DONE!" is in order. It's not uncommon to find that the threaded sets were never completely smooth. Especially on the more budget priced frames. And given that this is an older hiten frame if it's reasonably smooth then you're doing well.

There SHOULD be a range during tightening where you go from having a bit of slop to a smooth feel and then to the bearing notchiness that indicates too much preload. The tight but smooth portion would be there over at least a small range of tightening before it gets notchy. If it just goes directly from some play to notchy then there's still something greatly amiss in the system. It may be the steer tube or the ends of the head tube on the frame that are not dead on parallel.

Road Fan 11-17-09 03:39 PM

Quote:

Originally Posted by BCRider (Post 10040690)
Sounds like a "WELL DONE!" is in order. It's not uncommon to find that the threaded sets were never completely smooth. Especially on the more budget priced frames. And given that this is an older hiten frame if it's reasonably smooth then you're doing well.

There SHOULD be a range during tightening where you go from having a bit of slop to a smooth feel and then to the bearing notchiness that indicates too much preload. The tight but smooth portion would be there over at least a small range of tightening before it gets notchy. If it just goes directly from some play to notchy then there's still something greatly amiss in the system. It may be the steer tube or the ends of the head tube on the frame that are not dead on parallel.

Thanks, I appreciate that. I've done a lot of bike work in my long biking history, but no metal-bending.

Re the headset adjustment; the only ones I've found that do not have an "engagement" range are Campy old-style steel Records. Those seem to have a hair trigger, for loose to notchy. So this old French piece is not a major challenge. It's smooth but not like a Strada, but good enough. The bars turn freely and there's no play.

I also just got my Shimano 600 aluminum crank on it, using the original French cups and the Shimano spindle, added the old Shimano 600 derailleurs, and got at least the front brake and derailleur cabled and tuned. I'm also using 700c wheels with Shimano 600 hubs, and a 6-speed Shimano freewheel. I really will be able to see the effect of the frame and geometry alone.

Road Fan 11-17-09 03:40 PM

Quote:

Originally Posted by illwafer (Post 10040534)
if anyone cares, i straightened a steerer tube by inserting it between some tree branches and putting all my weight on it several times. i barely moved it anywhere, but i got it pretty close. it works fine, and i'm not worried about a catastrophe since i know how strong it is.

Good!

Reynolds 11-18-09 12:07 PM

They should have put the threaded cup on the steerer to avoid ovalizing it.

SJX426 11-18-09 01:58 PM

ANY ideas how to straighten this one?!

http://i985.photobucket.com/albums/a...n/P9051190.jpghttp://i985.photobucket.com/albums/a...n/P9051182.jpghttp://i985.photobucket.com/albums/a...n/P9051181.jpg

Road Fan 11-18-09 02:10 PM

Quote:

Originally Posted by Reynolds (Post 10049238)
They should have put the threaded cup on the steerer to avoid ovalizing it.

Yeah, hindsight is great, isn't it! I didn't even think of that since I didn't bring cup, just the fork. I'm not sure the tech thought of it either, he could have emailed me and asked me to bring it

Live and learn!

Road Fan 11-18-09 02:17 PM

All I can say is that your situation is much more complex than mine. First, you have Reynolds 531, which is a lot stronger and less ductile than the mild steel I have. It would have a higher tendency to work harden. Your bends are in the fork crown and in the fork blades. I'd definitely take this to a frames expert, rather than a better LBS like I did. If you have ready access to a replacement, maybe you should buy it.

BCRider 11-18-09 02:33 PM

Yeah, I think that the blue one is pretty much what the frame experts would term "dead meat on a stick".... :D

illwafer 11-23-09 12:27 PM

Quote:

Originally Posted by SJX426 (Post 10049852)
ANY ideas how to straighten this one?!

bend it!

give it a shot. if it's almost impossible to bend back (but possible), then it will be almost impossible to catastrophically break (but possible).

Sluggo 11-23-09 03:09 PM

Quote:

Originally Posted by SJX426 (Post 10049852)
ANY ideas how to straighten this one?!

This is a long ways from the gentle curve descibed in the original post. The steerer is kinked at the crown really bad. The blades might be salvageable, so it might be possible to replace the steerer, then straighten the blades. But it would be easier to replace the steerer, crown, blades, and dropouts at the same time.

operator 11-23-09 03:23 PM

You can straighten that by buying a new fork.

operator 11-23-09 03:24 PM

Quote:

Originally Posted by Sluggo (Post 10067956)
This is a long ways from the gentle curve descibed in the original post. The steerer is kinked at the crown really bad. The blades might be salvageable, so it might be possible to replace the steerer, then straighten the blades. But it would be easier to replace the steerer, crown, blades, and dropouts at the same time.

Doesn't make any sense to waste labour on something that costs $60 new.


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